Expo Aperture 2 depth of field guide : ExpoImaging, developer of camera accessories, including the ExpoDisc Digital White Balance Filter, today at Photokina announced the new ExpoAperture2 Depth-of-Field Guide, a pocket-sized circular calculator that enables photographers to determine the depth-of-field for a given focal length, aperture size, and sensor or film format. The ExpoAperture2 Depth-of-Field Guide has been improved to easily compensate for a camera's sensor or film size and to simplify its use over a wider range of focal lengths. The ExpoAperture2 Depth-of-Field Guide is printed front and back on three tough circular plastic discs that rotate against one another, functioning as a compact mechanical calculator.